Methods and apparatus to mitigate interference and to extend field of view in ultra-wideband systems

ABSTRACT

Methods and systems are described for generating a first filtered signal by passing signal energy in a first radio frequency (RF) spectral band associated with a signaling bandwidth of an ultra-wideband (UWB) RF signaling system, generating a second filtered signal by passing signal energy in a second RF spectral band associated with the signaling bandwidth of the UWB RF signaling system, generating a plurality of digitized streams of pulses by identifying RF pulses in a respective filtered signal above a respective predetermined threshold, generating at least one time-stamped tag data packet, based on decoding a valid over-the-air packet corresponding to a plurality of RF pulses received according to a known burst pattern, selecting a time-stamped tag data packet from the at least one received time-stamped tag data packet, formulating a network data packet based on the selected time-stamped tag data packet, and outputting the network data packet.

BACKGROUND

In some real-time location systems (RTLS), radio-frequencyidentification (RFID) tags are mounted to objects. The RFID tagstransmit data to a plurality of receivers. The transmissions areprocessed to determine locations of the objects.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The accompanying figures, where like reference numerals refer toidentical or functionally similar elements throughout the separateviews, together with the detailed description below, are incorporated inand form part of the specification, and serve to further illustrateembodiments of concepts that include the described embodiments, andexplain various principles and advantages of those embodiments.

FIG. 1 illustrates an example locating system in which examplesdisclosed herein may be implemented.

FIG. 2 is a block diagram representative of an example multipath signalprocessor (MSP) constructed in accordance with teachings of thisdisclosure.

FIG. 3 is a block diagram representative of an example multi-detectorfiltering and detection module constructed in accordance with teachingsof this disclosure.

FIG. 4 is a frequency spectrum illustrating overlapping filterbandwidths.

FIG. 5 is a frequency spectrum illustrating non-overlapping filterbandwidths.

FIG. 6 is a frequency spectrum illustrating overlapping filterbandwidths.

FIG. 7 illustrates a timing diagram for an RTLS tag transmission (TX) inan example high-resolution time-of-arrival (TOA) determination system.

FIG. 8 illustrates a timing diagram for an adjustable timing windowfunction.

FIG. 9 illustrates a timing diagram for a receiver (RX) fine timingwindow function.

FIG. 10 is a block diagram representative of an example receiverimplementing the example MSP of FIG. 2.

FIG. 11 is a block diagram representative of an example packet decoder.

FIG. 12 is a flowchart representative of an example method implemented,in accordance with teachings of this disclosure.

FIG. 13 is a flowchart representative of an example method implementedin accordance with teachings of this disclosure.

FIG. 14 is a first example receiver configuration constructed inaccordance with teachings of this disclosure.

FIG. 15 is a second example receiver configuration constructed inaccordance with teachings of this disclosure.

FIG. 16 is a block diagram representative of an example logic circuitcapable of implementing example methods and apparatus disclosed herein.

Skilled artisans will appreciate that elements in the figures areillustrated for simplicity and clarity and have not necessarily beendrawn to scale. For example, the dimensions of some of the elements inthe figures may be exaggerated relative to other elements to help toimprove understanding of embodiments.

The apparatus and method components have been represented whereappropriate by conventional symbols in the drawings, showing only thosespecific details that are pertinent to understanding the embodiments soas not to obscure the disclosure with details that will be readilyapparent to those of ordinary skill in the art having the benefit of thedescription herein.

DETAILED DESCRIPTION

Before proceeding with this detailed description, it is noted that theentities, connections, arrangements, and the like that are depictedin—and described in connection with—the various figures are presented byway of example and not by way of limitation. As such, any and allstatements or other indications as to what a particular figure“depicts,” what a particular element or entity in a particular figure“is” or “has,” and any and all similar statements—that may in isolationand out of context be read as absolute and therefore limiting—can onlyproperly be read as being constructively preceded by a clause such as“In at least one embodiment, . . . ” or “In at least one example, . . ..” And it is for reasons akin to brevity and clarity of presentationthat this implied leading clause is not repeated ad nauseum in thisdetailed description.

Moreover, any of the variations and permutations described herein can beimplemented with respect to any embodiments, including with respect toany method embodiments and with respect to any system embodiments.Furthermore, this flexibility and cross-applicability of embodiments ispresent in spite of the use of slightly different language (e.g.,process, method, steps, functions, set of functions, and the like) todescribe and or characterize such embodiments.

Real-time location systems (RTLS) are becoming increasingly popular,especially in sporting venues (e.g., football stadiums) for trackingplayers. In some RTLS, football players, for example, wearradio-frequency identification (RFID) tags that periodically send outover-the-air packets as consecutive ultra-wideband (UWB) radio frequency(RF) pulses. The RF pulses may be detected using detectors that comparereceived signal energy against a respective threshold level, to detectif a pulse is present. These UWB RF pulses often have a very widebandwidth, approximately in the 6.35-6.75 Gigahertz (GHz) range.However, many mobile devices operate in a range of approximately6.425-6.525 GHz. Examples of such mobile devices may include mobilevideo cameras. Further, it should be noted that this particular band mayalso be reserved for licensed operators, TV, or police. For example,services are authorized to use 6.425 to 6.525 GHz for mobile use underFCC parts 101.603, 74.602, 78.103, and fixed operations under 101.803.Systems described below may be configured to reject interference bysimultaneously processing multiple RF signal paths using filters ofvarying RF spectral bands.

Disclosed herein are example apparatuses, systems and methods fordetecting, for example, UWB transmissions using transceivers havingparallel RF signal processing paths. As disclosed herein, each signalpath may be processed differently so as to provide combined signalprocessing that results in improved detection of, for example, UWBtransmissions, through wider antenna coverage, enhanced noise reduction,or both.

To achieve the improved detection of transmissions, examples disclosedherein process each separate RF path with bandpass filters havingrespective bandwidths. In some examples, a given filter may have arelatively narrower bandwidth that attenuates signal energy in the knownfrequency band of an interfering system, such as the video camerasdescribed above. In such examples, the RF signal processing path havinga relatively narrower bandwidth may perform better than a full bandwidthfilter in the presence of a known interfering system. In particular, thenarrow bandwidth filter is preconfigured to remove signal energy atfrequencies (e.g., 6.425-6.525 GHz) associated with the interferingsystem. Further, overlapping filter bands allows for high sensitivity inthe absence of interference, as well as minimally reduced sensitivity inthe presence of interference.

In some examples, each RF signal processing path has a wide bandwidthfilter, covering approximately all of a spectral band of pulses emittedfrom the RFID tag, and each wide bandwidth filter receives signals fromseparate antennas. In such examples, a wider field-of-view isattainable, and an arbiter selects signals from one of the two widebandwidth filters. It should be noted that such systems may be used inscenarios where there is no significant interference from the knowninterfering system.

In some examples, at least two RF signal processing paths haverelatively narrow bandwidth filters, which may have a bandwidth ofapproximately 100-200 MHz as opposed to a relatively wider bandwidth ofapproximately 400 MHz wide. One of the narrow bandwidth filters may havea spectral band between 6.35-6.525 GHz while the other narrow bandwidthfilter has a spectral band between 6.55-6.75 GHz. Such examples may beuseful if the interfering signal energy from the interfering systemvaries over time. In some scenarios, a system may operate in a givenband of a plurality of available bands, which may be determined on “gameday,” for example, in which case an example using non-overlappingfilters (or partially overlapping filters) may continue to clearlyprocess the received bursts from the RFID tags.

In some examples, each of the bandpass filters is used to providefiltered signals to one or more detectors, which may be two-inputcomparators, for example, wherein the comparators are configured withappropriate thresholds for detecting UWB pulses. Packet decoders maythen analyze a digitized stream of pulses from the comparator outputs toidentify valid over-the-air packets prior to forwarding time-stamped tagdata packets that include information such as a tag identification, aburst identification, and a time stamp corresponding to when theover-the-air packet was received.

As described above, examples disclosed herein may provide numerousimprovements over existing systems, such as mitigating interference inthe presence of an interfering system. In some examples, if aninterfering system is not present, a wider field of view may beattainable through the simultaneous processing of filtered signalsreceived from additional antennas. Further, when using filters havingdifferent spectral bands, a wider bandwidth is available in the absenceof interference, and a narrower bandwidth is available in the presenceof interference. If interference is intermittent, it may be beneficialto overlap the spectral bands of the filters.

FIG. 1 is an exemplary RTLS, in accordance with some embodiments. Asdescribed in detail below in connection with FIGS. 7 and 8, the RTLS ofFIG. 1 includes RTLS tags 112 a-f that transmit blink data (e.g., UWBtransmissions) and receivers 113 a-l configured to receive the blinkdata. As described in detail below in connection with FIGS. 2, 7-11, thereceivers 113 a-l convey information associated with the blink data(e.g., time measurements, signal measurements, and the blink data) to acentral processor/hub 111, which identifies locations of thecorresponding RTLS tags 112 a-f. It should be noted that the blink dataand information associated with the blink data may take the form of anetwork data packet that is formulated based on a time-stamped tag datapacket.

In the illustrated example of FIG. 1, one or more of the receivers 113a-l implements a multipath signal processor (MSP) 200 constructed inaccordance with teachings of this disclosure. In FIG. 1, receiver 113 ais shown to include an MSP 200, however it should be noted that anycombination of receivers 113 a-l may include MSPs 200. The example MSP200 is configured to implement parallel processing of multiple RF signalprocessing paths to mitigate interference and provide broader coverage.FIG. 2 is a block diagram illustrating an example implementation of theMSP 200.

The example MSP 200 of FIG. 2 includes a first filtering and detectionmodule 222 a and a second filtering and detection module 222 b. Thefirst filtering and detection module 222 a includes a first filter 205 aand the second filtering and detection module 222 b includes a secondfilter 205 b. Further, the first filtering and detection module 222 aincludes a first detector 215 a and the second filtering and detectionmodule 222 b includes a second detector 215 b. In the example of FIG. 2,the first and second detectors 215 a and 215 b are shown as comparators,however additional or alternative detection components may be employed.For simplicity, components of known RF receivers (square-lawdemodulators, amplifiers, etc.) are not shown, but may be included inthe filter and detection blocks 222 a-b. The example MSP 200 of FIG. 2includes first and second packet decoders 220 a and 220 b, respectively.The example first and second decoders 220 a and 220 b are incommunication with the first and second detectors 215 a and 215 b,respectively. In the example of FIG. 2, the first and second packetdecoders 220 a and 220 b are coupled to an arbiter 225, which outputs aselected time-stamped tag data packet to packet formatter 235 fornetwork data packet generation.

While the example MSP 200 of FIG. 2 includes two (2) filtering anddetection modules 222 a-b, examples disclosed herein may include anysuitable number (e.g., three (3)) of filtering and detection modules, aswell as any suitable number of corresponding packet decoders 220.

In the illustrated example of FIG. 2, the first filter 205 a isconfigured to pass first signal energy in a first RF spectral bandassociated with a signaling bandwidth of an UWB RF signaling system, andto output a first filtered signal. The second filter 205 b is configuredto pass second signal energy in a second RF spectral band associatedwith the signaling bandwidth of the UWB RF signaling system, and tooutput a second filtered signal. In some embodiments, the first signalenergy is received from a first antenna and the second signal energy isreceived from a second antenna. Such embodiments may provide a widerfield of view. Alternatively, the first signal energy and the secondsignal energy are received from a common antenna.

The first and second detectors 215 a and 215 b receive the first andsecond filtered signals, respectively. Each of the first and seconddetectors 215 a and 215 b outputs a digitized stream of pulses byidentifying pulses in the corresponding filtered signal that are above arespective predetermined threshold V_(TH). In some examples, a givendetector may compare the respective received filtered signals againstvarious thresholds, as described in connection with FIG. 3. FIG. 3illustrates a multi-detector filter and detection block 322, inaccordance with some embodiments. The system shown in FIG. 3 mayrepresent filtering and detection block 222 a for example, having threedetectors 315 a-c, each processing the same filtered analog signalreceived from filter 305, connected to three packet decoding circuits220 (shown as packet decoding circuits 320 a-c in FIG. 3). As shown,each detector 315 a-c has a respective unique threshold V_(TH1),V_(TH2), and V_(TH3). Each threshold may be tuned for various SNRcharacteristics; for example, V_(TH1) may be sensitive in detectinglow-amplitude signals, but more erroneous (producing morefalse-positives), while V_(TH2) may be higher than V_(TH1), producefewer false-positives, but more accurately detecting larger magnitudesignals. FIG. 3 includes three parallel detection and packet decodingpaths, however it should be noted that this should not be consideredlimiting, and any number of parallel detection and packet-decoding pathsmay be included.

In such embodiments, the threshold value has tradeoffs betweensignal-to-noise ratio (SNR) and sensitivity. For example, detectors 315a and 315 b having thresholds V_(TH1) and V_(TH2) respectively, whereV_(TH1)<V_(TH2), detector 315 a may provide a higher sensitivity, at thecost of more false positive comparator “hits”. Alternatively, detector315 b may provide higher SNR, while having the tradeoff that some pulsesmay be missed. As each detector is processing the filtered signalreceived from filter 305, the arbiter will select the first time-stampedtag data packet available from packet decoders 320 a-c.

Each of the first and second packet decoders 220 a and 220 b isconfigured to receive a respective one of the digitized streams ofpulses and to decode a valid over-the-air packet corresponding to aplurality of RF pulses received according to a known burst pattern.Additionally, each of the first and second packet decoders 220 a and 220b is configured to generate a respective time-stamped tag data packetincluding (i) information in the valid over-the-air packet and (ii) acorresponding timestamp. In some embodiments, the corresponding timestamp represents an average of counter values in the respective receiverfor a plurality of detected RF pulses.

In the example of FIG. 2, the arbiter 225 is configured to receive atleast one time-stamped tag data packet from at least one of the firstand second packet decoders 220 a and 220 b, and to select a time-stampedtag data packet from the at least one received time-stamped tag datapacket. In some examples, the arbiter simply selects the firsttime-stamped tag data packet it receives. In scenarios where the firstfilter 205 a has a wide bandwidth and the second filter 205 b has anarrow bandwidth, the signal filtered by the first detector 205 a willarrive at the corresponding detector 215 a before the signal filtered bythe second filter 205 b, due to a group delay introduced to the secondfiltered signal as a result of the second filter 205 a having a narrowbandwidth. Thus, in the scenario where there is no interference, packetdecoder 220 a will produce a time-stamped tag data packet to arbiter 225before packet decoder 220 b. In the scenario where interference ispresent, packet decoder 220 a may not identify any valid over-the-airpackets, and the arbiter will select the time-stamped tag data packetfrom packet decoder 220 b, operating on the narrowly filtered signal. Inorder to prevent the group delay introduced by the narrow filter, theamount of group delay can be calculated and compensated for. Forexample, during final testing of a given MSP, time stamps can beobtained for inputs into the first and second filters, and an averagetime difference (e.g., the group delay value), can be obtained, andstored in memory to a resolution of ⅛ of a nanosecond. This is possibleas a time-of-arrival (TOA) circuit uses eight (8) samples to figure outthe fine time of a 1 nanosecond resolution. When normal production codeis running, the difference value may be entered into the fine timecalculation of the slower side, making it as if the packet appearedfaster than it really did. Thus, the difference in timestamps of widelyand narrowly filters is very small, and switching between inputs istransparent. Further, the central hub 111 will continue to calculateaccurate locations, regardless of which input was selected using arbiter225.

In some examples, the arbiter 225 is configured to send a reset commandto at least one of the first and second packet decoders 220 a and 220 bin response to the selection of the time-stamped tag data packet. Insome embodiments, the arbiter 225 is configured to send the resetcommand to the one of the packet decoders 220 a and 220 b that isassociated with the selected time-stamped tag data packet, so that thepacket decoders may begin decoding a new packet from a different RFIDtag, or a subsequent packet from the same RFID tag, for example. In someembodiments, the arbiter 225 is configured to send the reset command toall of the packet decoders, in case any packet decoders are in theprocess of decoding a duplicate packet. In some embodiments, the arbiter225 is configured to send the clear command to any of the packetdecoders 220 receiving the respective filtered signal associated withthe selected time-stamped tag data packet. In the above examples, thearbiter avoids selecting the same time-stamped tag data packet (e.g.,same tag ID, burst ID, etc.) that may have been simultaneously decodedin two parallel RF signal processing paths.

In some embodiments, the arbiter 225 is further configured to determinewhether the selected time-stamped tag data packet is a duplicate of atleast one stored time-stamped tag data packet. In such instances, packetformatter 235 may be configured to generate and to output a network datapacket corresponding to the selected time-stamped tag data packet if thetime-stamped tag data packet is not a duplicate, as the central hub forcalculating position may only use one timestamp for a given packet froma given RFID tag. In such examples, the arbiter may hold onto previouslyreceived time-stamped tag data packets, and may check (e.g., tag ID,burst ID) of incoming time-stamped tag data packets against thepreviously received time-stamped tag data packets. If the incomingtime-stamped tag data packet is a duplicate of a previously receivedtime-stamped tag data packet, then the arbiter discards the duplicate.The amount of time each previously received time-stamped tag data packetis retained may vary depending on application. In such examples, aplurality of registers or a more sophisticated memory device may be usedto retain the previously received time-stamped tag data packets, aswould be known to those of skill in the art.

In the example of FIG. 2, the packet formatter 235 is configured toformulate a network data packet based on the selected time-stamped tagdata packet, and to output the network data packet.

In some embodiments, the first filter 205 a has a RF spectral band ofapproximately all of the signaling bandwidth of the UWB RF signalingsystem, and the second filter 205 b has a RF spectral band covering aportion of the RF spectral band of the first filter 205 a, the RFspectral band of the second filter attenuating signal energy in a RFspectral band of a known interfering system. In such embodiments, in thepresence of interference, the signal being filtered by filter 205 a andpresented to detector 215 a may be interfered with, and packet decoder220 a may not detect a valid over-the-air packet. Meanwhile filter 205 bis processing the signal received from the antenna, and is filtering outany interference provided by the known interfering system. Detector 215b then provides a digitized stream of pulses to packet decoder 220 b,which may then decode a valid over-the-air packet, and create atime-stamped tag data packet to provide to arbiter 225.

FIG. 4 is a diagram of a frequency spectrum of a UWB RF signalingsystem, in accordance with some embodiments. As shown, a signalingbandwidth 405 of the UWB RF signaling system spans approximately6.35-6.75 GHz, however this should not be considered limiting. In someembodiments, as shown in FIG. 4, the first filter 205 a has a passband410 of approximately all of the signaling BW of the UWB RF signalingsystem, while the second filter 205 b has a passband 415 covering aportion of the first filter 205 a. As shown, the passband 415 of thesecond filter 205 b lies outside of a known interfering band 420. Insome embodiments, the known interfering band 420 may be associated withknown RF bands of common interfering devices, such as mobile videocameras. As shown, the known interfering band 420 spans approximatelyfrom 6.425 GHz to 6.525 GHz, while the second filter passband 415 spansapproximately from 6.55 GHz to 6.75 GHz, thus attenuating any signalenergy present from any present interferers.

In some embodiments, the first and the second filters havenon-overlapping RF spectral bands, the RF spectral bands of the firstand second filters collectively making up approximately all of thesignaling bandwidth of UWB RF signaling system. Such embodiments mayreject interfering systems that have varying spectral bands, or one of aplurality of interfering systems each having different spectral bands(e.g., mobile phones, radios, etc).

FIG. 5 illustrates an alternative embodiment for passbands of the firstfilter 205 a and the second filter 205 b. As shown, the first and secondfilters 205 a and 205 b have narrow, non-overlapping passbands 510 and515, respectively. Specifically, first filter 205 a has a RF spectralband 510 of approximately 6.35 GHz to 6.525 GHz, and second filter 205 bhas a RF spectral band 515 of approximately 6.55 GHz to 6.75 GHz. Insuch embodiments, the known interfering band may move about thesignaling BW of the UWB RF signaling system throughout a given period oftime. Thus, if the known interfering band occupies a region associatedwith the passband of the first filter 205 a, the second filter 205 b mayprovide a clear received signal from RF tags, and vice versa.

In some embodiments, the first and second filters 205 a and 205 b haveRF spectral bands over approximately all of the signaling bandwidth ofthe UWB RF signaling system. In such embodiments, the MSP 200 may beconfigured to provide a wider field of view by connecting each filter todifferent antennas. In the absence of any interference, each signal maybe processed accurately, and the arbiter 225 would continue to selectthe first received time-stamped tag data packet for transmission to thecentral hub. FIG. 6 is a frequency spectrum illustrating such anembodiments having overlapping spectral bands. As shown in FIG. 6, thefirst filter 205 a and second filter 205 b have passbands 610 and 615,respectively, each spanning approximately all of the signaling BW of theUWB RF signaling system (−6.35 GHz to 6.75 GHz). Such embodiments may beadvantageous when each filter is connected to a respective antenna, asthe use of two (or possibly more) antennas provides a wider effectivefield of view, which using the same architecture as previously describedproduces what may be known as a diversity receiver.

FIG. 1 illustrates an example locating system 100 in which methods andapparatus to mitigate interference and/or extend a field of view may beimplemented, using the MSPs 200 as described above. The example locationsystem 100 of FIG. 1 calculates a location of an object by anaccumulation, at a central processor/hub 111, of location data or timeof arrivals (TOAs) associated with the object. In the example locatingsystem 100 of FIG. 1, the TOAs represent a relative time of flight (TOF)from real-time location service (RTLS) tags 112 a-f as recorded at oneor more of a plurality of receivers 113 a-l (e.g., UWB readers).Receivers 113 a-l may include the components described above withrespect to MSPs 200, as well as various additional components. A timingreference clock is used, in some examples, such that at least a subsetof the receivers 113 a-l may be synchronized in frequency, whereby therelative TOA data associated with each of the RTLS tags 112 a-f may beregistered by a counter associated with at least a subset of thereceivers 113 a-l. In some examples, a reference tag 114 a-b (e.g., aUWB transmitter) positioned at known coordinates, is used to determinean offset between the counters associated with at least a subset of theof the receivers 113 a-l. In the example of FIG. 1, the RTLS tags 112a-f and the reference tags 114 a-b reside in an active RTLS field 118.The systems described herein may be referred to as either“multilateration” or “geolocation” systems, terms that refer to theprocess of locating a signal source by solving an error minimizationfunction of a location estimate determined by the difference in time ofarrival (DTOA) between TOA signals received at multiple ones of thereceivers 113 a-l.

In some examples, the locating system 100 including at least the tags112 a-f and the receivers 113 a-l is configured to provide twodimensional and/or three dimensional precision localization (e.g.,subfoot resolutions), even in the presence of multipath interference,due in part to the use of short (e.g., nanosecond) duration pulses, theTOF of which can be accurately determined using detection circuitry,such as in the receivers 113 a-l. In some examples, the receivers 113a-l trigger on the leading edge of a received waveform. In someexamples, the short pulse characteristic of the pulses allows data to beconveyed by the system at a higher peak power, but lower average powerlevels, than a wireless system configured for high data ratecommunications, yet still operate within local regulatory requirements.

In some examples, to provide a preferred performance level whilecomplying with the overlap of regulatory restrictions (e.g., FCC andETSI regulations), the tags 112 a-f may operate with an instantaneous −3dB bandwidth of approximately four hundred (400) megahertz (MHz) and anaverage transmission below one-hundred eighty-seven (187) pulses in aone (1) millisecond (msec) interval, provided that the rate issufficiently low. In such examples, the predicted maximum range of thesystem, operating with a center frequency of 6.55 gigahertz (GHz), isroughly two-hundred (200) meters in instances in which a twelve (12) dbidirectional antenna is used at the receiver, but the projected rangewill depend, in other examples, on receiver antenna gain. Alternativelyor additionally, the range of the system allows for one or more tags 112a-f to be detected with one or more receivers positioned throughout afootball stadium used in a professional football context. Such aconfiguration advantageously satisfies constraints applied by regulatorybodies related to peak and average power densities (e.g., effectiveisotropic radiated power density (“EIRP”)), while still optimizingsystem performance related to range and interference. In some examples,tag transmissions with a −3 dB bandwidth of approximately four hundred(400) MHz yields an instantaneous pulse width of roughly two (2)nanoseconds (nsec) that enables a location resolution to better thanthirty (30) centimeters (cm).

In the illustrated example of FIG. 1, the object to be located carries atag 112 a-f (e.g., a tag having a UWB transmitter). The object carriesthe tag 112 a-f via, for example, an attachment of the tag 112 a-f tothe object, adhering the tag 112 a-f to the object, inserting the tag112 a-f into an article associated with the object such as clothing orshoulder pads and/or any other suitable manner of carrying. In theexample of FIG. 1, the tag 112 a-f transmits a burst pattern (e.g.,multiple pulses at a one (1) megabits per second (Mb/s) burst rate, suchas one-hundred twelve (112) bits of On-OFF keying (OOK) at a rate of one(1) Mb/s), and optionally, a burst pattern including an informationpacket utilizing OOK that may include, but is not limited to, IDinformation, a sequential burst count or other desired information forobject or personnel identification, inventory control, etc. In someexamples, the sequential burst count (e.g., a packet sequence number)from each tag 112 a-f may be advantageously provided in order to permit,at the central processor/hub 111, correlation of TOA measurement datafrom different ones of the receivers 113 a-l.

In some examples, the tag 112 a-f employs UWB waveforms (e.g., low datarate waveforms) to achieve fine resolution because of their short pulse(i.e., sub-nanosecond to nanosecond, such as a 2 nsec (one (1) nsec upand one (1) nsec down)) durations. As such, the information packet maybe of a short length (e.g. one-hundred twelve (112) bits of OOK at arate of one (1) Mb/sec, in some examples), that advantageously enables ahigher packet rate. If each information packet is unique, a higherpacket rate results in a higher data rate. If each information packet istransmitted repeatedly, the higher packet rate results in a higherpacket repetition rate. In some examples, higher packet rate repetitionrate (e.g., twelve (12) hertz (Hz)) and/or higher data rates (e.g., one(1) Mb/sec, two (2) Mb/sec or the like) for each tag may result inlarger datasets for filtering to achieve a more accurate locationestimate. Alternatively or additionally, in some examples, the shorterlength of the information packets, in conjunction with other packetrate, data rates and other system functionality, may result in a longerbattery life (e.g., seven (7) years battery life at a transmission rateof one (1) Hz with a three-hundred (300) milliamp-hour (mAh) cell). Analternate implementation may be a generic compact, three (3) volt coincell, series no. CR2032, with a battery charge rating of two-hundredtwenty (220) mAhr, whereby the latter generic coin cell, as can beappreciated, may provide for a shorter battery life.

Tag signals may be received at a receiver 113 a-l directly from RTLStags 112 a-f, or may be received after being reflected en route.Reflected signals travel a longer path from the RTLS tag to the receiver113 a-l than would a direct signal, and are thus received later than thecorresponding direct signal. This delay is known as an echo delay ormultipath delay. 112 a-f If reflected signals are sufficiently strongenough to be detected by the receiver 113 a-l, they can corrupt a datatransmission through inter-symbol interference. Reflected signals can beexpected to become weaker as delay increases due to more reflections andthe longer distances traveled. Thus, beyond some value of inter-pulsetime (e.g., nine-hundred ninety-eight (998) nsec), corresponding to somepath length difference (e.g., 299.4 m), there will be no advantage tofurther increases in inter-pulse time (and, hence lowering of burst datarate) for any given level of transmit power. In this manner,minimization of packet duration allows the battery life of a tag to bemaximized, since its digital circuitry need only be active for a brieftime. Different environments can have different expected echo delays, sothat different burst data rates and, hence, packet durations, may beappropriate in different situations depending on the environment.

Reduction or minimization of the packet duration allows a tag 112 a-f totransmit more packets in a given time period, although in practice,regulatory average EIRP limits may often provide an overridingconstraint. However, brief packet duration also reduces the likelihoodof packets from multiple tags overlapping in time, causing a datacollision. Thus, minimal packet duration allows multiple tags 112 a-f totransmit a higher aggregate number of packets per second, allowing forthe largest number of tags 112 a-f to be tracked, or a given number oftags 112 a-f to be tracked at the highest rate.

In some examples, sensor telemetry data may be transmitted from the tag112 a-f to provide the receivers 113 a-l with information about theenvironment and/or operating conditions of the tag 112 a-f. For example,the tag 112 a-f may transmit a temperature to the receivers 113 a-l.Such information may be valuable, for example, in a system involvingperishable goods or other refrigerant requirements. In this exampleembodiment, the temperature may be transmitted by the tag 112 a-f at alower repetition rate than that of the rest of the data packet. Forexample, the temperature may be transmitted from the tag 112 a-f to thereceivers 113 a-l at a rate of one time per minute (e.g., one (1)TX/min), or in some examples, once every seven-hundred twenty (720)times the data packet is transmitted, whereby the data packet in thisexample is transmitted at an example rate of twelve (12) TX/sec.

In some examples, the tag 112 a-f is programmed to intermittentlytransmit data to the receivers 113 a-l in response to a signal from amagnetic command transmitter (not shown). The magnetic commandtransmitter may be a portable device, functioning to transmit aone-hundred twenty-five (125) kilohertz (kHz) signal, in some examples,with a range of approximately fifteen (15) feet or less, to one or moreof the tags 112 a-f. In some examples, the tags 112 a-f may be equippedwith at least a receiver tuned to the magnetic command transmittertransmit frequency (e.g., one-hundred twenty-five (125) kHz) andfunctional antenna to facilitate reception and decoding of the signaltransmitted by the magnetic command transmitter.

In some examples, one or more (preferably four or more) other tags, suchas the reference tags 114 a-b in FIG. 1, are positioned within and/orabout the monitored region 118. In some examples, the reference tag 114a-b is configured to transmit a signal that is used to measure therelative phase (e.g., the count of free-running counters) ofnon-resettable counters within the receivers 113 a-l.

In some examples, the receivers 113 a-l are connected in a “daisy chain”119 fashion to advantageously allow for a large number of receivers 113a-l to be interconnected over a significant monitored region 118 toreduce and simplify cabling, reduce latency, provide power, and/or thelike. Each of the receivers 113 a-l includes one or more filters and oneor more detectors for receiving and processing transmissions, such asUWB transmissions, and preferably, a packet decoding circuit thatextracts a time of arrival (TOA) timing pulse train, transmitter ID,packet number, and/or other information that may have been encoded inthe tag transmission signal (e.g., material description, personnelinformation, etc.) and is configured to sense signals transmitted by thetags 112 a-f and one or more reference tags 114 a-b. Example filters anddetectors disclosed herein for receiving and processing suchtransmissions are described in detail below.

In the illustrated example of FIG. 1, each receiver 113 a-l includes atime measuring circuit that measures times of arrival (TOA) of tagbursts, with respect to its internal counter. The time measuring circuitis phase-locked (e.g., relative phase differences do not change andtherefore respective frequencies are identical) with a common digitalreference clock signal distributed via cable connection from the centralprocessor/hub 111 having a central timing reference clock generator. Thereference clock signal establishes a common timing reference for thereceivers 113 a-l. Thus, multiple time measuring circuits of therespective receivers 113 a-l are synchronized in frequency, but notnecessarily in phase. While there typically may be a phase offsetbetween any given pair of receivers in the receivers 113 a-l, the offsetis readily determined through use of one or more of the reference tags114 a-b. Alternatively or additionally, each receiver 113 a-l may besynchronized wirelessly via virtual synchronization without a dedicatedphysical timing channel.

In some example embodiments, the receivers 113 a-l are configured todetermine attributes of the received signal. In the illustrated exampleof FIG. 1, as measurements are determined at each receiver 113 a-l in adigital format, rather than analog, signals are transmittable to thecentral processor/hub 111. Advantageously, because packet data andmeasurement results can be transferred at high speeds to a receivermemory, the receivers 113 a-l can receive and process tag (andcorresponding object) locating signals on a nearly continuous basis. Assuch, in some examples, the receiver memory allows for a high burst rateof tag events (i.e., information packets) to be captured.

Data cables or wireless transmissions may convey measurement data fromthe receivers 113 a-l to the central processor/hub 111 (e.g., the datacables may enable a transfer speed of two (2) Mbps). In some examples,measurement data is transferred to the central processor/hub 111 atregular polling intervals.

In the illustrated example, the central processor/hub 111 determines orotherwise computes a tag location (i.e., object location) by processingTOA measurements relative to multiple data packets detected by thereceivers 113 a-l. In some examples, the central processor/hub 111 isconfigured to resolve the coordinates of a tag 112 a-f using nonlinearoptimization techniques.

In some examples, TOA measurements from multiple receivers 113 a-l areprocessed by the central processor/hub 111 to determine a location of atag 112 a-f by a differential time-of-arrival (DTOA) analysis of themultiple TOAs. The DTOA analysis includes a determination of tagtransmit time to, whereby a time-of-flight (TOF), measured as the timeelapsed from the estimated tag transmit time to to the respective TOA,represents graphically the radii of spheres centered at respectivereceivers 113 a-l. The distance between the surfaces of the respectivespheres to the estimated location coordinates (x₀, y₀, z₀) of thetransmit tag 112 a-f represents the measurement error for eachrespective TOA, and the minimization of the sum of the squares of theTOA measurement errors from each receiver participating in the DTOAlocation estimate provides for the location coordinates (x₀, y₀, z₀) ofthe transmit tag 112 a-f and of that tag's transmit time to.

In some examples, the system described herein may be referred to as an“over-specified” or “over-determined” system. As such, the centralprocessor/hub 111 may then calculate one or more valid (i.e., mostcorrect) locations based on a set of measurements and/or one or moreincorrect (i.e., less correct) locations. For example, a location may becalculated that is impossible due the laws of physics or may be anoutlier when compared to other locations. As such one or more algorithmsor heuristics may be applied to minimize such error. The starting pointfor the minimization may be obtained by first doing an area search on acoarse grid of x, y and z over an area defined by the user and followedby a localized steepest descent search. The starting location for thisalgorithm is fixed, in some examples, at the mean position of all activereceivers. In some examples, no initial area search is needed, andoptimization proceeds through the use of a Davidon-Fletcher-Powell (DFP)quasi-Newton algorithm. In other examples, a steepest descent algorithmmay be used. In each case, the algorithms may be seeded with an initiallocation estimate (x, y, z) that represents the two-dimensional (2D) orthree-dimensional (3D) mean of the positions of the receivers 113 a-lthat participate in the tag location determination.

One example algorithm for error minimization, which may be referred toas a time error minimization algorithm, is described in Equation 1:

$\begin{matrix}{ɛ = {\sum\limits_{j = 1}^{N}\; \left\lbrack {\left\lbrack {\left( {x - x_{j}} \right)^{2} + \left( {y - y_{j}} \right)^{2} + \left( {z - z_{j}} \right)^{2}} \right\rbrack^{\frac{1}{2}} - {c\left( {t_{j} - t_{0}} \right)}} \right\rbrack^{2}}} & (1)\end{matrix}$

Where N is the number of receivers, c is the speed of light, (X_(j),y_(j), Z_(j)) are the coordinates of the j^(th) receiver, t_(j) is thearrival time at the j^(th) receiver, and to is the tag transmit time.The variable to represents the time of transmission. Since to is notinitially known, the arrival times, t_(j), as well as t₀, are related toa common time base, which in some examples, is derived from the arrivaltimes. As a result, differences between the various arrival times havesignificance for determining location as well as t₀.

In some examples, the locating system 100 comprises a receiver grid,whereby each of the receivers 113 a-l in the receiver grid keeps areceiver clock that is synchronized, with an initially unknown phaseoffset, to the other receiver clocks. The phase offset between anyreceivers may be deteiniined by use of the reference tag 114 a-b that ispositioned at a known coordinate position (x_(T), y_(T), z_(T)). Thephase offset serves to resolve the constant offset between counterswithin the receivers 113 a-l, as described below.

In some examples, a number N of receivers 113 a-l {R_(j): j-1, . . . ,N} positioned at known coordinates (x_(Rj), y_(Rj), z_(Rj)), which arerespectively located at distances d_(Rj) from a reference tag 114 a-b,such as given in Equation 2:

d _(R) _(j) =√{square root over ((x)}_(R) _(j) −x _(T))²+(y _(R) _(j) −y_(T))²+(z _(R) _(j) −Z _(T))²   (2)

Each receiver R_(Rj) utilizes, for example, a synchronous clock signalderived from a common frequency time base, such as clock generator.Because the receivers are not synchronously reset, an unknown, butconstant offset O_(j) exists for each receiver's internal free runningcounter. The value of the constant offset O_(j) is measured in terms ofthe number of fine resolution count increments (e.g., a number ofnanoseconds for a one nanosecond resolution system).

The reference tag 114 a-b is used, in some examples, to calibrate theradio frequency locating system as follows: The reference tag 114 a-bemits a signal burst at an unknown time τ_(R). Upon receiving the signalburst from the reference tag 114 a-b, a count N_(R) _(j) as measured atreceiver R_(j) is given in Equation 3 by:

N _(R) _(j) =βτ_(R) +O _(j) +βd _(R) _(j) /c   (3)

Where c is the speed of light and β is the number of fine resolutioncount increments per unit time (e.g., one per nanosecond). Similarly,each object tag T_(i) of each object to be located transmits a signal atan unknown time τ_(i) to produce a count N_(i) _(j) as given in Equation4:

N _(i) _(j) =βτ_(i) +O _(j) +βd _(i) _(j) /c   (4)

At receiver R_(j) where d_(i) _(j) is the distance between the objecttag T_(i) and the receiver 113 a-l R_(j). Note that τ_(i) is unknown,but has the same constant value for all receivers. Based on theequalities expressed above for receivers R_(j) and R_(k) and given thereference tag 114 a-b information, phase offsets expressed asdifferential count values are determined as given in Equations 5a-b:

$\begin{matrix}{{{N_{R_{j}} - N_{R_{k}}} = {\left( {O_{j} - O_{k}} \right) + {{\beta \left( {\frac{d_{R_{I}}}{c} - \frac{d_{R_{k}}}{c}} \right)}\mspace{14mu} {or}}}},} & \left( {5a} \right) \\{\left( {O_{j} - O_{k}} \right) = {{\left( {N_{R_{j}} - N_{R_{k}}} \right) - {\beta \left( {\frac{d_{R_{I}}}{c} - \frac{d_{R_{k}}}{c}} \right)}} = \Delta_{j_{k}}}} & \left( {5b} \right)\end{matrix}$

Where Δ_(j) _(k) is constant as long as d_(R) _(j) -d_(R) _(k) remainsconstant, (which means the receivers 113 a-l and reference tag 114 a-bare fixed and there is no multipath situation) and β is the same foreach receiver 113 a-l. Note that Δ_(j) _(k) is a known quantity, sinceN_(R) _(j) , N_(R) _(k) , β, d_(R) _(j) /c, and d_(R) _(k) /c are known.That is, the phase offsets between receivers R_(j) and R_(k) may bereadily determined based on the reference tag transmissions. Thus, againfrom the above equations, for a tag 112 a-f (T_(i)) transmissionarriving at receivers R_(j) and R_(k), one may deduce the followingEquations 6a-b:

$\begin{matrix}{{N_{i_{j}} - N_{i_{k}}} = {{\left( {O_{j} - O_{k}} \right) + {\beta \left( {\frac{d_{i_{j}}}{c} - \frac{d_{i_{k}}}{c}} \right)}} = {\Delta_{j_{k}} + {{\beta \left( {\frac{d_{i_{j}}}{c} - \frac{d_{i_{k}}}{c}} \right)}\mspace{14mu} {or}}}}} & \left( {6a} \right) \\{\mspace{79mu} {{d_{i_{j}} - d_{i_{k}}} = {\left( {c\text{/}\beta} \right)\left\lfloor {N_{i_{j}} - N_{i_{k}} - \Delta_{j_{k}}} \right\rfloor}}} & \left( {6b} \right)\end{matrix}$

Each arrival time, t_(j), can be referenced to a particular receiver(receiver “1”) as given in Equation 7:

$\begin{matrix}{t_{j} = {\frac{1}{\beta}\left( {N_{j} - \Delta_{j\; 1}} \right.}} & (7)\end{matrix}$

The minimization, described in Equation 1, may then be performed overvariables (x, y, z, t₀) to reach a solution (x′, y′, z′, t₀′). FIG. 7shows an example timing diagram 700 for an RTLS tag transmission (TX) ina high-resolution TOA determination system. The example timing diagram700 includes a TX clock 701, a preamble 710, and a data packet 720,which as presented in FIG. 7, includes the preamble 710 as a subset ofthe data packet 720. The preamble 710 is composed of a transmit (TX)series of pulses 711T, wherein the TX series of pulses 711T are equallyspaced in time, in accordance with a period associated with the TX clock701. In some examples, the period associated with the TX clock isapproximately one (1) microsecond (μsec), whereby the TX clock 701operates at a frequency of one (1) MHz.

Each individual TX pulse 711T′ in the TX series of pulses 711T isidentical. In some examples, the TX pulse 711T′ includes a six (6) GHzcarrier wave modulated by a two (2) nsec pulse, such as a triangular orrectangular function (rect). In some examples, the TX pulse 711T′ isadditionally shaped at a receiver 113 a-l by a transmit and receiveantenna and any electronics associated with an amplification orpre-amplification of the TX pulse 711T′, in conjunction with thehigh-resolution TOA determination system. In some examples, the TX pulse711T′ shape at the receiver 113 a-l, denoted RX pulse 711R′, may beconsistent with a function ˜t e^(−t/τ). The TX series of pulses 711T isused to provide for an iterative windowing function, such as, forexample, an adjustable coarse timing window 800, which is describedbelow in connection with FIG. 8.

The data packet 720 includes at least the following data words: theaforementioned preamble 710, a sync code 712, a header 720A, a transmitidentification (TX ID) 120B, and a CRC word 120C. The sync code 712represents a known sequence of 1's and 0's. In some examples, the 1'sand 0's may be distributed in other ways. In some examples, the synccode 712 is sixteen (16) bits long. In the illustrated example, the synccode 712 consists primarily of 1's, which represent the TX pulses711T′—rather than 0's, which represent ‘blanks,’ or no pulse. The synccode 712 is used to provide for a registration code 950 in response toeach of the TX pulses 711T′ associated with the sync code 712, wherebythe registration code 850 provides for a record of a detection of thesync code 712 in a receiver (RX) fine timing window function 900, whichis described below in connection with FIG. 9.

The data packet 720 is transmitted by the RTLS tag transmitter, in someexamples, continually and periodically. In some examples, thetransmission of the data packet 720 is initiated immediately at the endof the one (1) μsec period associated with a final transmit bit, whichin this example is the least significant bit of CRC 720 c. In someexamples, a waiting period between successive transmissions isestablished.

In some examples, the over-the-air data packet 720 is one-hundred twelve(112) bits long, wherein the bit distribution may be as follows: thepreamble 710 (e.g., thirty-two (32) bits), the sync code 712 (e.g.,sixteen (16) bits), the header 720A (e.g., sixteen (16) bits), the TX ID720 b (e.g., thirty-two (32) bits), and the CRC 720C (e.g., sixteen (16)bits). In some examples, a transmission time associated with the datapacket 720 and the aforementioned one (1) MHz data rate is one-hundredtwelve (112) μsec. In this example, when coupled with a thirty-two (32)μsec preamble 710, a data RTLS tag transmission time may be calculatedto be one-hundred forty-four (144) μsec per transmission, or one-hundredforty-four (144) μsec/TX. With a data rate equal to 144 μsec/TX, asdescribed in this example, it may be possible to accommodate up toten-thousand (10,000) transmissions (e.g., single transmissionsassociated with up to ten-thousand 10,000 RTLS tags in thehigh-resolution TOA determination system) in just over one (1) second.

In other examples, the data packet 720 may consist of a plurality ofdata long words 720B′, immediately following the TX ID 720B andpreceding the CRC 720C, resulting in a longer data packet 720. In someexamples, the plurality of data long words 720B′ are each thirty-two(32) bits long.

In some examples, the plurality of data long words 720B′ may include oneor more of a temperature, an acceleration, and an attitude of rotationaldisplacement. In some examples, the plurality of data long words 720B′may include a ‘Query’ command to the receiver, wherein the RTLS tagtransmitter, in this example, is equipped with a one-hundred twenty-five(125) KHz receiver and associated firmware to decode a response.

FIG. 8 shows an example timing diagram for a receiver (RX) adjustablecoarse timing window function 800. The example timing diagram of FIG. 8includes the TX clock 701 and the TX series of pulses 711T associatedwith the RTLS tag transmission (TX) 700, presented in FIG. 7, and an RXclock 801 and an RX clock timing diagram 802. A received (RX) pulsetrain 811R is composed of a series of the RX pulses 711R, corresponds tothe TX series of pulses 711T, and is synchronized to the RX clock 801,which is resident at an example receiver 113 a-l in the receiver grid.An RX pulse signature 812, representing an earliest pulse 815 and aseries of echoes 816 a-b and possible noise pulses 817, as shown in FIG.8, is associated with the RX clock timing diagram 802, and is alsoassociated with the corresponding TX pulse 711T′.

In the example presented in FIG. 8, the one (1) MHz TX clock 701, aspresented in FIG. 7, and the associated one (1) MHz RX clock 801 may beout of phase with respect to each other. The relative stability of therespective TX clock 701 and RX clock 801 frequencies for the shortduration TX transmit time allows for an iterative, adaptive adjustmentof the RX clock 801 phase with respect to the TX clock 701 phase,effecting a change in the receiver RX adjustable coarse timing windowfunction 800.

The example RX adjustable coarse timing window function 800 of FIG. 8,is composed of a series of detection windows 820, including widedetection windows 821-823 and narrow detection windows 831 and 833, andan associated set of functions to adaptively position the series of wideand narrow detection windows 820 to center the RX pulse 711R in thecorresponding window. In the example of FIG. 8, there are three (3) widedetection windows 821-823 and two (2) narrow detection windows 831 and833, however this should not be considered limiting. For notationconvenience, the last window in the series of wide and narrow detectionwindows 820 is called a final detector window.

In the example of FIG. 8, a first detection window 821 may be centeredat four-hundred eighty (480) nsec, for example, with a width ofone-hundred (150) nsec. The center of the first detector window is afunction of a first registered detection, wherein the present exampleregisters a first registered detection at a second echo 816 b of the RXpulse 711R. In some examples, the width of the first detection window821 is a function of an expected distance from the RTLS tag transmitterto the receiver 113 a-l, the distance-to-time relationship given by theRF propagation time—the speed of light in a vacuum (c)—approximately one(1) foot per nsec.

The first wide detection window 821 may be adaptively updated by asecond wide detection window 822 as provided by evidence of a secondregistered detection, wherein the present example registers a secondregistered detection at a first echo 816 a of the RX pulse 711R. In theexample of FIG. 8, the second wide detection window 822 is centered atapproximately four-hundred sixty (460) nsec with a width of one-hundredfifty (150) nsec. Similarly, the second wide detection window 822 may beadaptively updated by a third detection window 823 as provided byevidence of a third registered detection, wherein the present exampleregisters a third registered detection at an earliest pulse 815 of theRX pulse 711R. In the example embodiment, the third detection window 823may be centered at approximately four-hundred fifteen (415) nsec with awidth of one-hundred fifty (150) nsec.

The series of wide detection windows 821-823 continue to be adaptivelyupdated by the registered detections of RX pulses 711R that include theRX pulse train 811R corresponding to the TX series of pulses 711T in thepreamble 710. In some examples, a final wide detector window 823 isdeclared after a detection of ten (10) RX pulses 711R. At which point afinal wide detector window 823 is determined, the registered detectionsfor the series of wide detection windows 821-823 ends, and the series ofnarrow detection windows 831-833 is implemented.

In the example of FIG. 8, a first narrow detection window 831 iscentered at the center of wide detection window 823. The width of thefirst narrow detection window 831 is thirty (30) nsec, in some examples.Note that, as the example of FIG. 8 demonstrates, a timing shift mayresult with the registered detection of the RX pulse 711R associatedwith the final wide detection window 833. The placement of the firstnarrow detection window 831, centered at four-hundred twenty-five (425)nsec-, graphically represents such a shift, as the earliest pulse 815associated with the RX pulse 711R appears to be registered along the RXclock timing diagram 802 closer to four-hundred fifteen (415) nsec.

Each of the series of narrow detection windows 831 and 833 is composedof three (3), ten (10) nsec, disjoint timing windows 831 a-c and 833 a-c(see FIG. 9). Detections for the RX pulses 711R that include the RXpulse train 811R are registered in parallel in each of the threedisjoint timing windows 831 a-c, for example, to determine to which ofthe three disjoint timing windows 831 a-c the detection should beassigned. The purpose of the series of narrow detection windows 831 and833 is to ensure that the final detection associated with the final RXpulse 711R in the RX pulse train 811R is registered in a final centerdisjoint timing window 833 b associated with the final detector window833. A slide narrow window function 835 to slide the series of narrowdetection windows left and right in ten (10) nsec increments, forexample, is provided as a method to achieve the aforementionedrequirement, and as such the final detection associated with the finalRX pulse 711R in the RX pulse train 811R is registered in the center ofthe final detector window 833.

The example RX adjustable coarse timing window function 800 of FIG. 8,may be implemented as a first feedback loop, wherein a pulse detectorresides in the forward feed and the slide window function 835 mayinclude the feedback. The pulse detector may determine whether or notpulse detection is registered in the currently prescribed disjointtiming windows 831 a-c, for example, for any of the series of narrowdetection windows 831 and 833. As a function of the detectionsregistered in the currently prescribed disjoint timing windows 831 a-c,for example, a feedback function may determine which direction a shiftis to be made, and in some examples, what is the magnitude of theprescribed shift, if different from a default shift value of ten (10)nsec, for example.

As previously stated, the default shift magnitude is equal to the shiftmagnitude presented in the example given in FIG. 8, that of ten (10)nsec, for example. A minimum shift magnitude may also be given (e.g.,ten (10) nsec). Larger shift magnitudes may be incorporated, dependenton the detection algorithm. In some examples, a detection algorithm thatmay determine multiple echoes 816 a-b as registered in a relatively widedetector window may include logic to ‘skip’ left over severalreflections at once to expedite the capture of the earliest pulse 815,the line-of-sight channel. In such instances, a registration of multipleechoes 816 a-b in the relatively wide detector window may be determinedby the relative amplitude of the registered detections.

Multiple echoes 816 a-b or reflections may be registered in the samedetector window in, for example, reflective environments, such asenvironments surrounded by conductors. By contrast, it is unlikely thatboth the earliest pulse 815, the line-of-sight channel, and an echo 816a-b or reflection might arrive within the limits of the same widedetector window 821-823, as the time difference between the earliestpulse 815, the line-of-sight channel, and the echo 816 a-b, thereflection, may be on the order of tens of feet, or greater thanone-hundred (150) nsec difference in TOA, the width of the wide detectorwindows in this example.

Further, the detectors themselves may include several functions that mayaffect an improved detection resolution. For example, the detectors maybe assigned a detection level or a threshold level that may determinewhether the magnitude of the earliest pulse 815, one or more of theechoes 816 a-b, or a noise pulse 817 is in fact a signal, or just alow-level background noise interference. Alternatively or additionally,for example, a signal-to-noise (SNR) level may be monitored dynamically,and the detection threshold level adjusted accordingly. In a furtheradvancement, a relative strength of the signal may be monitoreddynamically, whereby the strength of the signal, in conjunction with aTOA determination associated with the signal, may include two inputs toan automatic gain control (AGC) for either a pre-amplification or anamplification of the signal.

FIG. 9 shows an example timing diagram for a receiver (RX) fine timingwindow function 900. FIG. 9 includes the final detector window 833 andthe three (3), ten (10) nsec disjoint timing windows 833 a-c associatedwith the final detector window 833, and a parallel set of fine detectorwindows 940. The final detector window 833 and the fine detector windows940 are synchronized with the RX clock timing diagram 802, as shown inFIG. 8. The leading edge of a first fine detector window 940/00 issynchronous with the leading edge of the final center disjoint timingwindow 833 b associated with the final detector window 833. The RX finetiming window function 900 includes registering a series of detectionsin the parallel set of fine detector windows 940, each associated withthe final center disjoint timing window 833 b. The series of detectionsin the parallel set of fine detector windows 940 provides for adetection record of the sync code 712, the sequence of 1's and 0's TXpulses 711T transmitted by the RTLS tag transmitter.

The registering the series of detections in the parallel set of finedetector windows 940, each associated with the final center disjointtiming window 833 b, includes a generation of the registration code 850which codifies the detections of the RX pluses 711R associated with thesync code 712 TX pulses 711T. The registration code 950 codifies thedetections with respect to each of the fine detector windows940/00-940/09 that include the set of fine detector windows 940, asshown in the example given in FIG. 9. As demonstrated for the exampleillustrated in FIG. 9, each successive fine detector window940/00-940/09 overlaps the previous fine detector window 940/00-940/09by one (1) nsec, and each of the fine detector windows 940/00-940/09 inthe parallel set of fine detector windows 940 is ten (10) nsec wide.

As represented by the registration code 950 for the example of FIG. 9, adetection of the RX pulse 711R associated with the corresponding synccode 712 TX pulse 711T is registered in the fine detector windows940/00-940/04, but no detection is registered in the fine detectionwindows 940/05-940/09. As such, it is inferred, in such instances, thatthe TOA for the RX pulse 711R is four-hundred fourteen (414) nsec afterthe leading edge of the RX clock 801.

FIG. 10 is a block diagram representative of an example receiver 113 ina UWB receiver system (e.g., the locating system 100 of FIG. 1) thatimplements the example MSP 200 of FIG. 2. In some embodiments,over-the-air data packets 720 as shown in FIG. 7 are transmitted to thereceiver 113 and received by at least one UWB antenna 1021. In theexample of FIG. 10, the MSP 200 implemented by the receiver 113 includesat least two filtering and detection modules 222, at least two packetdecoders 220, and an arbiter 225, which are configured as describedabove in connection with FIG. 2. In some embodiments, each of thefiltering and detection modules 222 receives an analog signal from thesame antenna 1021 (as shown in FIG. 10). Additionally, in some examples,bandwidths filtered by the different individual filtering and detectionmodules 222 vary to block specific interference, as described below inmore detail with respect to FIG. 15. In alternative embodiments, such aswhen no interference is anticipated (e.g., by an entity tasked withconfiguring the locating system 100) at least two of the filtering anddetection modules 222 receive analog signals from two different UWBantennas, thereby extending a field-of-view for the receiver 113, asdescribed above with respect to FIG. 4.

In some embodiments, each of the filtering and detection modules 222that receives a respective analog signal from an antenna generates oneor more digitized streams of pulses (e.g., using the comparators 215 a,215 b for example), for decoding by the packet decoders 220. As shown inFIG. 10, there are two digitized stream sets, 1023 a and 1023 b, howeverit should be noted that there might be more than two filtering anddetection modules 222 and, thus, more than two digitized streams ofpulses 1023. As shown in FIG. 10, the digitized streams 1023 a and 1023b are n wires wide and m wires wide, respectively. In some embodiments,a first one of the filtering and detection modules 222 includes nparallel, concurrent, independent detectors 215 functioning with ndistinct threshold levels, configured to provide n digital data streams1023 a to a respective set of n packet decoders 220 (see description ofFIG. 14 for more detail). Further, a second one of the filtering anddetection modules 222 has m parallel, concurrent, independent detectors215 functioning with m distinct threshold levels, configured to providem digital data streams 1023 b to a respective set of m packet decoders220. In some embodiments, n and/or m is greater than or equal one. Insome embodiments, n equals m. In alternative embodiments, n may notnecessarily equal m. The various thresholds may be used to providedifferent sensitivities to noise and SNR, as described above. As shownin FIG. 10, there are n+m packet decoders 220, each operating on arespective digitized stream of pulses from a respective detector. Thatis to say each digitized stream is independently processed in parallel(as shown in FIG. 14). In some embodiments, the threshold levels appliedto analog signal stream in the filtering and detection modules 222 aredetermined according to a function of a signal-to-noise ratio (SNR)present in the communication channel. In some embodiments, theindividual threshold levels are set dynamically as a function of one ormore of an antenna preamp gain and an estimated RTLS tag range. In someembodiments, the thresholds may be set at final test (e.g., calibration)for the various detectors according to noise level, and stored for lateruse. In some embodiments, the threshold values depend on RF gain andtemperature. In some embodiments, a temperature compensation isperformed by adjusting a baseband attenuator. In some embodiments, RTLStag range may be restricted by adjusting RF gain on the receiver.

The packet decoders 220 perform two or more parallel, concurrent,identical signal-processing functions on the two or more sets of digitaldata streams 1023 a-b. The two or more packet decoders 220 may beconfigured to receive valid over-the-air data packets 720 (FIG. 7) thatcorrespond to RTLS tags 112 a-f (FIG. 1) in the form of digitized streamprovided by the detectors 215 in the filtering and detection module 222.In some examples, the packet decoders 220 may provide for a packetframing and extraction function as part of a data recovery circuit,whereby an RTLS tag 112 a-f identification may be extracted. The RTLSidentification may be extracted by the TX identification field 720 b ofthe data packet 720, as described previously.

The packet decoding circuits 220 may process two or more parallel,concurrent, identical valid over-the-air data packets 720 from RLTS tags112 a-f. The data packet framing and extraction function, and the UWBTOA calculation function may each provide for a registration of eachsignal received at the filtering and detection blocks 222 with anindexed TOA and corresponding RTLS tag identification, the correspondingpacket decoding circuits 220 and the corresponding time-stamped tag datapacket 720. The time-stamped tag data packets are sent by TOA line 1025to an arbiter 225. A packet decoding circuit 220 is described in moredetail below with respect to FIG. 7.

In the example of FIG. 10, the arbiter 225 selects a time-stamped tagdata packets received via the TOA lines 1025 provided by the packetdecoders 220. The example arbiter 225 of FIG. 10 selects the TOA line1025 that converges to the earliest TOA from the up to two or morepacket decoders 220 driven by the sets of digital data streams 1023 a-b.

The example arbiter 225 of FIG. 10 performs a tag queue function,whereby each of the time-stamped tag data packets is identified by anidentifier associated with an RTLS tag 112 a-f and an associated TOA.The tag queue function performs a formatting and ordering of thecollection of RTLS tag identifiers and TOAs, effectively a first-infirst-out (FIFO) memory buffer awaiting a transmission to the centralprocessor/hub 111. Upon the tag queue function trigger, a time-stampedtag data packet 1027 is sent to a formatting and data coding/decodingfunction 235 that, in turn, repackages the time-stamped tag data packet1027 and transmits a network data packet 1030 b to the centralprocessor/hub 111 (FIG. 1).

In some embodiments the network data packet may be transmitted over aconventional Ethernet LAN connection to the central processor/hub 111.In some embodiments, the network data packet 1030 b transmitted by theformatting and data coding/decoding function 235 to the centralprocessor/hub 111 may be synchronized by a ten (10) MHz receiver clock1040, received from the previous receiver clock in the “daisy chain”119, and transmitted to the next receiver clock in the “daisy chain” 119following a synchronous frequency up/down convert. The receiver clock1040 drives a phase-locked loop (PLL) 1041, whereby a frequency dividerin a feedback loop in conjunction with a voltage-controlled oscillator(VCO) provides a one-hundred (100) MHz receiver clock 1042 that issynchronized in phase to the ten (10) MHz receiver clock 1040. Theone-hundred (100) MHz receiver clock 1042 is provided to synchronize alllogic blocks in the receiver 113. The one-hundred (100) MHz receiverclock 1042 provides for the parallel set of fine detector windows 940, abasis of a set of receiver timing windows used to capture and registerpulses transmitted by RTLS tags 112 a-f in the TOA determination, asdescribed previously with respect to FIG. 9.

A second function of the formatting and data coding/decoding function235 is a buffering, reformatting, and repeating of central processordata received 1030 a and transmitted 1030 b between the receiver 113 andthe central processor/hub 111 via the “daisy chain” 119 receivernetwork. The central processor data 1030 a-b received and transmittedfrom and to the formatting and data coding/decoding function 235 mayinclude a series of commands that are decoded at a command decoder 1044to trigger receiver functions. Examples of such functions include anauto/manual control function 1020, a series of telemetry functions 1060,and pruning (e.g., by the arbiter 225) a data queue and to manage,delete, and reorder the data queue. The auto/manual control function1020 may be commanded (e.g., from manual mode) to report sensorinformation such as, for example, temperature and/or other telemetrydata recorded in the telemetry function 1060, and may be commanded tomanually adjust one or more of an antenna preamp gain and the previouslydescribed threshold levels of the filtering and detection modules 222.

A power supply 1050 may be configured to power the receiver 113 by wayof an AC-DC convertor, whereby the AC power may be provided as an inputfrom the central processor/hub 111. The power supply 1050 may beaccompanied, in some embodiments, by a power delay circuit 1051 to allowfor an orderly ‘power up’ of sequential receivers 113 a-l, thus avoidinga power surge and over-current event in the central processor data 1030a-b transmission lines.

In some example embodiments, the UWB receiver system transmits packetdata and measurement results at high speeds to TOA measurement bufferswithin the arbiter 225, such that the receivers 113 a-l can receive andprocess tags 112 a-f (and corresponding object) locating signals on anearly continuous basis. That is, multiple valid time-stamped datapackets 720 can be processed in close succession, thereby allowing theuse of hundreds to thousands of tag transmitters.

In some embodiments, data stored in TOA measurement buffers implantedby, for example, the arbiter 225, is sent to a central processor/hub111, over the central processor data transmission lines 1030 a-b inresponse to a specific request from the central processor/hub 111.

In some embodiments, the collection of the central processor data 1030a-b transmission lines connecting the “daisy chain” 119 network ofreceivers 113 a-l is composed of two bi-directional data links. In someembodiments, these data links may be RS422 differential serial links. Anetwork interface may receive command signals from a centralprocessor/hub 111 on one link, for example, to instruct a transfer ofthe TOA measurement buffer to the central processor/hub 111. Additionalcommands may include those to adjust one or more operatingcharacteristics or parameters of the filtering and detection modules 222such as gain and/or detection thresholds used by the detectors 215. Thebi-directional data links may also provide for buffer for data signalslinked between “daisy chain” 119 receivers 113 a-l, buffering sequentialtransmissions between the present and next receivers 113 a-l in acommunications chain.

The synchronous frequency up/down convert performed on the ten (10) MHzreceiver clock 1040 provides a driver for the receiver clock 1040transmitted to the next reader in the “daisy chain” 119. An advantage ofthis approach, in some examples, is that the ten (10)MHz receiver clock1040 transmitted to the next receiver, as with the original ten (10)MHzreceiver clock 1040, may be made low enough in frequency so that it canbe transmitted over low-cost cables (e.g., twisted pair wires). Astiming jitter of the local timing reference signal degrades as an PLLmultiplier coefficient is increased, there is a necessary trade-offbetween frequency and jitter of the local timing reference signal andthe frequency of the timing reference clock.

Utilizing a common ten (10)MHz receiver clock 1040 for timing reference,a plurality of local timing reference signals (one in each receiver) canbe precisely matched in frequency. Using this approach, additionalreceivers can be connected without concern for clock loading. Bufferdelay is also not an issue since the timing reference clock is used forfrequency only, and not phase reference.

In some embodiments, the ten (10)MHz receiver clock 1040 may includedifferential signals. The use of differential clock signals isadvantageous since they avoid clock duty cycle distortion, which canoccur with the transmission of relatively high-speed clocks (e.g., >ten(10)MHz) on long cables (e.g., >one-hundred (100) feet).

FIG. 11 is a block diagram representative of an example implementationof the packet decoder 220 disclosed above. In some examples, the packetdecoder 220 includes a windowing/gating function 1171, a TOA function1172, a window control clock and data recovery (PLL) function 1173, aTOA averaging function 1174, a data sync and extract function (1 MHz-7MHz) 1175-1176, a tag data recovery and processing function 1177, and adelay compensation circuit 1178. The packet decoder 225 processes thedigital data stream 1023 received from one of the filtering anddetection modules 222, as shown in FIG. 10, to provide an unpacked datapacket and the TOA associated with the RTLS tag to the arbiter 225.

The windowing/gating function 1171 and the window control clock and datarecovery clock PLL 1173 work as a feedback loop to recover the TX clock701 and provide for the adjustable coarse timing window function 800, aspresented in FIG. 8 and described previously. The TOA function 1172works in conjunction with the one-hundred (100) MHz receiver clock 1042.The RX clock 801 provides for a TOA coarse time associated with theadjustable coarse timing window function 800, shown in FIG. 8, byregistering detections for the RX pulses 711R that include the RX pulsetrain 811R corresponding to the TX pulses 711T in the series of TXpulses 711 in the preamble 710. The parallel set of fine detectorwindows 940 provides a TOA fine time associated with the fine timingwindow function 900, shown in FIG. 9, by recording detections by aregistration code 950 for the RX pulses 711R that include the sync code712 TX pulses 711T. The description for the adjustable coarse windowingfunction 800 and the fine timing window function 900 are givenpreviously with the presentation of FIGS. 8-9, respectively.

The TOA fine time the registration code 950, and the final coarsedetector window 830, as determined by the adjustable coarse timingwindow function 800, are sent to the TOA averaging function 1174, alongwith a latch TOA control signal indicating the end of a TOAdetermination. Further, in packet decoders 220 operating on narrowlyfiltered signals, a delay compensation module may provide TOA averagingfunction 1174 with a group delay value to calculate TOA. As previouslydescribed, the group delay value that results from the narrow filteringmay be obtained by comparing timestamps of the same signal processed bya narrow filter and a wide filter. This group delay value may then bestored in a memory in delay compensation module 1178, and used whencalculating the TOA. Thus, the TOA of a narrowly filtered signal will besimilar to that of a widely filtered signal, and the centralprocessor/hub 111 will continue to calculate accurate locations,regardless of whether the signal was narrowly or widely filtered. TheTOA averaging function 1174 is activated by a calculate TOA trigger, andthe averaged TOA is then sent to the tag data recovery and processingfunction 1177.

The data sync and extract function (1 MHz-2 MHz) 1175-1176 is triggeredupon phase lock of the PLL associated with the window control clock anddata recovery (PLL) function 1173. Upon data synchronization, the datapackets 720 are extracted and unpacked at a rate of 1 Mbps or 2 Mbps,and sent to the tag data recovery and processing function 1177. The tagdata recovery and processing function 1177 serves as a communicationscontrol function associated with the arbiter 225, shown in FIGS. 2 and10. The tag data recovery and processing function 1177 also serves as acontroller for the timing of a locking/unlocking of the window/gatingfunction and PLL 1173 and a triggering of the TOA averaging function1174.

FIG. 12 is a flowchart representative of an example method 1200including operations performed by, for example, the example MSP 200 ofFIG. 2. In the example method 1200, at block 1202, filter 205 agenerates a first filter signal by passing signal energy in a firstradio frequency (RF) spectral band associated with a signaling bandwidthof an ultra-wideband (UWB) RF signaling system. At block 1204, filter205 b generates a second filtered signal by passing signal energy in asecond RF spectral band associated with the signaling bandwidth of theUWB RF signaling system. At block 1206, detectors 215 a and 215 bgenerate a plurality of digitized streams of pulses, each respectivedigitized stream of pulses generated by identifying RF pulses in arespective filtered signal above a respective predetermined threshold.At block 1210, a plurality of packet decoders (e.g., 220 a-b) generateat least one time-stamped tag data packet, wherein a respectivetime-stamped tag data packet is generated by decoding a validover-the-air packet corresponding to a plurality of RF pulses receivedaccording to a known burst pattern at block 1208. The respectivetime-stamped tag data packet includes (i) information in the validover-the-air packet and (ii) a corresponding timestamp. At block 1212,an arbiter 225 selects a time-stamped tag data packet from the at leastone received time-stamped tag data packet. At block 1214, a packetformatter 235 formulates a network data packet based on the selectedtime-stamped tag data packet, and outputs the network data packet.

In some embodiments, the arbiter 225 sends a reset command to at leastone of the plurality of packet decoders in response to the selection ofthe time-stamped tag data packet, for example, to prevent any of thepacket decoders from processing duplicate packets.

In some embodiments, the arbiter 225 checks if the selected time-stampedtag data packet is a duplicate of at least one stored time-stamped tagdata packet, and outputs a network data packet corresponding to theselected time-stamped tag data packet if the time-stamped tag datapacket is not a duplicate.

In some embodiments, the first filter 205 a has a RF spectral band ofapproximately all of the signaling bandwidth of the UWB RF signalingsystem, and the second filter 205 b has a RF spectral band covering aportion of the RF spectral band of the first filter 205 a, the RFspectral band of the second filter 205 b attenuating signal energy in aRF spectral band of a known interfering system, as illustrated by thefrequency spectrum of FIG. 4. In some embodiments, the first and thesecond filters 205 a and 205 b have non-overlapping RF spectral bands,the RF spectral bands of the first and second filters 205 a and 205 bcollectively making up approximately all of the signaling bandwidth ofUWB RF signaling system, as illustrated by the frequency spectrum ofFIG. 5. In some embodiments, the first filter 205 a and second filter205 b have RF spectral bands over approximately all of the signalingbandwidth of the UWB RF signaling system, as illustrated by thefrequency spectrum of FIG. 6.

In some embodiments, the corresponding time stamp represents an averageof counter values in the respective receiver for a plurality of detectedRF pulses.

In some embodiments, the plurality of detectors 215 a-b includecomparators, each respective comparator configured to receive arespective filtered signal and a predetermined threshold V_(TH) asinputs. Further, it should be noted that the detectors 215 a-b may alsoinclude components for extracting modulation from the RF signal, such assquare-law demodulators for creating baseband pulses out of the RFbursts, as well as amplification elements to amplify the baseband pulsesprior to being received by the comparator.

In some embodiments, the first filtered signal is received from a firstantenna, and the second filtered signal is received from a secondantenna. In some embodiments, the first and second filtered signals arereceived from a common antenna.

FIG. 13 illustrates a flowchart of a process 1300, in accordance withsome embodiments. As shown in FIG. 13, first and second filtered signalsare generated at steps 1302 and 1304, respectively using filters 205 aand 205 b. RF energy pulses are detected from each filtered signal atsteps 1306 and 1308, respectively using detectors 215 a and 215 b. Atsteps 1310 and 1312, each detected stream of RF pulses is analyzed for avalid over-the-air packet using packet decoders 220 a and 220 b, usingmethods described above in connection with FIGS. 7-4. If a validover-the-air packet is identified, a time-stamped tag data packet isgenerated using a respective packet decoder 220 at least in part basedon information in the valid over-the-air packet and by adding atimestamp at 1316 and 1318. If no valid over-the-air packet isidentified, then the current RF energy pulse is disregarded at 1314. Atsteps 1320 and 1322, an arbiter 225 receives each time-stamped tag datapacket, and decides if the received time-stamped tag data packet is thefirst time seeing the received time-stamped tag data packet. In someexamples, the arbiter 225 clears one or more packet decoders uponreceiving a time-stamped tag data packet, while in alternativeembodiments, the arbiter 225 retains a history of received time-stampedtag data packets, and compares any received time-stamped tag datapackets against prior received time-stamped tag data packets usinginformation such as based on tag IDs, etc. If it is the first timeseeing the received time-stamped tag data packet, a network data packetis formulated and output from a packet formatter 235 at block 1326, thenetwork packet formulated based on the received time-stamped tag datapacket. If time-stamped tag data packet with the same tag ID has beenreceived prior, the received packet may be discarded 1324.

FIGS. 14 and 15 illustrate two configurations of a receiver 113, inaccordance with some embodiments. As shown, FIG. 14 includes a low-noiseamplifier (LNA) 1402, receiving a signal from antenna ANTI. The analogsignal is separately filtered using first and second filters 1405 a and1405 b, and passed to detectors 1415, which pass digital streams ofdetected RF pulses for packet processing, selection, and formatting1430. It should be noted that the components shown in FIGS. 14 and 15may take a similar form as the components described with respect to FIG.2, such as filters 205 a-b, detectors 215 a-b, and packet decoders 220,and processing and selection bock 1430 including arbiter 225 and packetformatter 235.

FIG. 15 illustrates an alternative configuration of a receiver withrespect to FIG. 14. As shown, FIG. 15 includes two LNAs 1502 a and 1502b, receiving signals from separate antennas ANT1 and ANT2, respectively.First filter 1505 a receives a signal from LNA 1502 a and produces afirst filtered signal while second filter 1505 b receives a signal fromLNA 1502 b, and produces a second filtered signal. The signals are thendetected 1415 and processed/selected 1430 in similar ways describedabove with respect to FIGS. 2, 10-11. In some embodiments, theconfiguration shown in FIG. 15 may have similar filter passbands asdescribed with respect to FIGS. 4-5.

FIG. 16 is a block diagram representative of an example logic circuitthat may utilized to implement, for example, one or more components ofthe example MSP 200 of FIG. 2 or, more generally, the example receiver113 of FIG. 10. The example logic circuit of FIG. 16 is a processingplatform 1600 capable of executing instructions to, for example,implement the example operations represented by the flowcharts of thedrawings accompany this description.

The example processing platform 1600 of FIG. 16 includes a processor1602 such as, for example, one or more microprocessors, controllers,field-programmable gate arrays (FPGA) and/or any suitable type ofprocessor. The example processing platform 1600 of FIG. 16 includesmemory (e.g., volatile memory, non-volatile memory) 1604 accessible bythe processor 1602 (e.g., via a memory controller). The exampleprocessor 1602 interacts with the memory 1604 to obtain, for example,machine-readable instructions stored in the memory 1604 correspondingto, for example, the operations represented by the flowcharts of thisdisclosure. Additionally or alternatively, machine-readable instructionscorresponding to the example operations of the flowcharts may be storedon one or more removable media (e.g., a compact disc, a digitalversatile disc, removable flash memory, etc.) that may be coupled to theprocessing platform 1600 to provide access to the machine-readableinstructions stored thereon.

The example processing platform 1600 of FIG. 16 includes a networkinterface 1606 to enable communication with other machines via, forexample, one or more networks. The example network interface 1606includes any suitable type of communication interface(s) (e.g., wiredand/or wireless interfaces) configured to operate in accordance with anysuitable protocol(s).

The example processing platform 1600 of FIG. 16 includes input/output(I/O) interfaces 1608 to enable receipt of user input and communicationof output data to the user.

The above description refers to block diagrams of the accompanyingdrawings. Alternative implementations of the examples represented by theblock diagrams include one or more additional or alternative elements,processes and/or devices. Additionally or alternatively, one or more ofthe example blocks of the diagrams may be combined, divided, re-arrangedor omitted. Components represented by the blocks of the diagrams areimplemented by hardware, software, firmware, and/or any combination ofhardware, software and/or firmware. In some examples, at least one ofthe components represented by the blocks is implemented by a logiccircuit. As used herein, the term “logic circuit” is expressly definedas a physical device including at least one hardware componentconfigured (e.g., via operation in accordance with a predeterminedconfiguration and/or via execution of stored machine-readableinstructions) to control one or more machines and/or perform operationsof one or more machines. Examples of a logic circuit include one or moreprocessors, one or more coprocessors, one or more microprocessors, oneor more controllers, one or more digital signal processors (DSPs), oneor more application specific integrated circuits (ASICs), one or morefield programmable gate arrays (FPGAs), one or more microcontrollerunits (MCUs), one or more hardware accelerators, one or morespecial-purpose computer chips, and one or more system-on-a-chip (SoC)devices. Some example logic circuits, such as ASICs or FPGAs, arespecifically configured hardware for performing operations (e.g., one ormore of the operations represented by the flowcharts of thisdisclosure). Some example logic circuits are hardware that executesmachine-readable instructions to perform operations (e.g., one or moreof the operations represented by the flowcharts of this disclosure).Some example logic circuits include a combination of specificallyconfigured hardware and hardware that executes machine-readableinstructions.

The above description refers to flowcharts of the accompanying drawings.The flowcharts are representative of example methods disclosed herein.In some examples, the methods represented by the flowcharts implementthe apparatus represented by the block diagrams. Alternativeimplementations of example methods disclosed herein may includeadditional or alternative operations. Further, operations of alternativeimplementations of the methods disclosed herein may combined, divided,re-arranged or omitted. In some examples, the operations represented bythe flowcharts are implemented by machine-readable instructions (e.g.,software and/or firmware) stored on a medium (e.g., a tangiblemachine-readable medium) for execution by one or more logic circuits(e.g., processor(s)). In some examples, the operations represented bythe flowcharts are implemented by one or more configurations of one ormore specifically designed logic circuits (e.g., ASIC(s)). In someexamples the operations of the flowcharts are implemented by acombination of specifically designed logic circuit(s) andmachine-readable instructions stored on a medium (e.g., a tangiblemachine-readable medium) for execution by logic circuit(s).

As used herein, each of the terms “tangible machine-readable medium,”“non-transitory machine-readable medium” and “machine-readable storagedevice” is expressly defined as a storage medium (e.g., a platter of ahard disk drive, a digital versatile disc, a compact disc, flash memory,read-only memory, random-access memory, etc.) on which machine-readableinstructions (e.g., program code in the form of, for example, softwareand/or firmware) can be stored. Further, as used herein, each of theterms “tangible machine-readable medium,” “non-transitorymachine-readable medium” and “machine-readable storage device” isexpressly defined to exclude propagating signals. That is, as used inany claim of this patent, none of the terms “tangible machine-readablemedium,” “non-transitory machine-readable medium,” and “machine-readablestorage device” can be read to be implemented by a propagating signal.

As used herein, each of the terms “tangible machine-readable medium,”“non-transitory machine-readable medium” and “machine-readable storagedevice” is expressly defined as a storage medium on whichmachine-readable instructions are stored for any suitable duration oftime (e.g., permanently, for an extended period of time (e.g., while aprogram associated with the machine-readable instructions is executing),and/or a short period of time (e.g., while the machine-readableinstructions are cached and/or during a buffering process)).

Although certain example apparatus, methods, and articles of manufacturehave been disclosed herein, the scope of coverage of this patent is notlimited thereto. On the contrary, this patent covers all apparatus,methods, and articles of manufacture fairly falling within the scope ofthe claims of this patent.

We claim:
 1. An apparatus comprising: a first filter configured to passsignal energy in a first radio frequency (RF) spectral band associatedwith a signaling bandwidth of an ultra-wideband (UWB) RF signalingsystem, and to output a first filtered signal; a second filterconfigured to pass signal energy in a second RF spectral band associatedwith the signaling bandwidth of the UWB RF signaling system, and tooutput a second filtered signal; a plurality of detectors, eachrespective detector configured to receive a respective filtered signaland to output a digitized stream of pulses by identifying pulses in thefiltered signal that are above a respective predetermined threshold; aplurality of packet decoders, each respective packet decoder configuredto receive a respective digitized stream of pulses and to decode a validover-the-air packet corresponding to a plurality of RF pulses receivedaccording to a known burst pattern, and to generate a respectivetime-stamped tag data packet comprising (i) information in the validover-the-air packet and (ii) a corresponding timestamp; an arbiter incommunication with the plurality of packet decoders, the arbiterconfigured to: receive at least one time-stamped tag data packet from atleast one of the plurality of packet decoders; select a time-stamped tagdata packet from the at least one received time-stamped tag data packet;and a packet formatter configured to formulate a network data packetbased on the selected time-stamped tag data packet, and to output thenetwork data packet.
 2. The apparatus of claim 1, wherein the arbiter isconfigured to send a reset command to at least one of the plurality ofpacket decoders in response to the selection of the time-stamped tagdata packet.
 3. The apparatus of claim 1, wherein the arbiter is furtherconfigured to check if the selected time-stamped tag data packet is aduplicate of at least one stored time-stamped tag data packet, and togenerate and to output a network data packet corresponding to theselected time-stamped tag data packet if the time-stamped tag datapacket is not a duplicate.
 4. The apparatus of claim 1, wherein thefirst filter and second filter have RF spectral bands over approximatelyall of the signaling bandwidth of the UWB RF signaling system.
 5. Theapparatus of claim 1, wherein the first filter has a RF spectral band ofapproximately all of the signaling bandwidth of the UWB RF signalingsystem, and wherein the second filter has a RF spectral band covering aportion of the RF spectral band of the first filter, the RF spectralband of the second filter attenuating signal energy in a RF spectralband of a known interfering system.
 6. The apparatus of claim 5, whereinthe RF spectral band of the first filter is approximately 6.35-6.75Gigahertz (GHz), the RF spectral band of the second filter isapproximately 6.55-6.75 GHz, and wherein the RF spectral band of theknown interfering system is approximately 6.425-6.525 GHz.
 7. Theapparatus of claim 1, wherein the first and the second filters havenon-overlapping RF spectral bands, the RF spectral bands of the firstand second filters collectively making up approximately all of thesignaling bandwidth of UWB RF signaling system.
 8. The apparatus ofclaim 7, wherein the first RF spectral band is approximately 6.35-6.525Gigahertz (GHz), and wherein the second RF spectral band isapproximately 6.55-6.75 GHz, and wherein an interfering system has an RFspectral band in either the first or second RF spectral band.
 9. Theapparatus of claim 1, wherein the corresponding time stamp represents anaverage of counter values in the respective receiver for a plurality ofdetected RF pulses.
 10. The apparatus of claim 1, wherein each detectorcomprises a comparator configured to receive the respective filteredsignal and the respective predetermined threshold as inputs, and tooutput the digitized stream of pulses.
 11. A method comprising:generating a first filtered signal by passing signal energy in a firstradio frequency (RF) spectral band associated with a signaling bandwidthof an ultra-wideband (UWB) RF signaling system; generating a secondfiltered signal by passing signal energy in a second RF spectral bandassociated with the signaling bandwidth of the UWB RF signaling system;generating, using a plurality of detectors, a plurality of digitizedstreams of pulses, each respective digitized stream of pulses generatedby identifying RF pulses in a respective filtered signal above arespective predetermined threshold; generating, using a plurality ofpacket decoders, at least one time-stamped tag data packet, wherein arespective time-stamped tag data packet is generated based on decoding avalid over-the-air packet corresponding to a plurality of RF pulsesreceived according to a known burst pattern, the respective time-stampedtag data packet comprising (i) information in the valid over-the-airpacket and (ii) a corresponding timestamp; receiving, at an arbiter incommunication with the plurality of packet decoders, the at least onetime-stamped tag data packet from at least one of the plurality ofpacket detectors; selecting a time-stamped tag data packet from the atleast one received time-stamped tag data packet; formulating, using apacket formatter, a network data packet based on the selectedtime-stamped tag data packet; and outputting the network data packet.12. The method of claim 11, further comprising sending a reset commandto at least one of the plurality of packet decoders in response to theselection of the time-stamped tag data packet.
 13. The method of claim11, wherein the method further comprises checking if the selectedtime-stamped tag data packet is a duplicate of at least one storedtime-stamped tag data packet, and outputting a network data packetcorresponding to the selected time-stamped tag data packet if thetime-stamped tag data packet is not a duplicate.
 14. The method of claim11, wherein the first filter and second filter have RF spectral bandsover approximately all of the signaling bandwidth of the UWB RFsignaling system.
 15. The method of claim 11, wherein the first filterhas a RF spectral band of approximately all of the signaling bandwidthof the UWB RF signaling system, and wherein the second filter has a RFspectral band covering a portion of the RF spectral band of the firstfilter, the RF spectral band of the second filter attenuating signalenergy in a RF spectral band of a known interfering system.
 16. Themethod of claim 15, wherein the RF spectral band of the first filter isapproximately 6.35-6.75 Gigahertz (GHz), the RF spectral band of thesecond filter is approximately 6.55-6.75 GHz, and wherein the RFspectral band of the known interfering system is approximately6.425-6.525 GHz.
 17. The method of claim 11, wherein the first and thesecond filters have non-overlapping RF spectral bands, the RF spectralbands of the first and second filters collectively making upapproximately all of the signaling bandwidth of UWB RF signaling system.18. The method of claim 17, wherein the first RF spectral band isapproximately 6.35-6.525 Gigahertz (GHz), and wherein the second RFspectral band is approximately 6.55-6.75 GHz, and wherein an interferingsystem has an RF spectral band in either the first or second RF spectralband.
 19. The method of claim 11, wherein the corresponding time stamprepresents an average of counter values in the respective receiver for aplurality of detected RF pulses.
 20. The method of claim 11, wherein theplurality of detectors are comparators, each respective comparatorconfigured to receive a respective filtered signal and a predeterminedthreshold as inputs.